Coral reefs, vital ecosystems supporting diverse marine life, are primarily shaped by the clonal expansion of coral colonies. Although the principles of coral clonal growth, involving polyp division for spatial extension, are well-understood, numerical modelling efforts are notably scarce in the literature. In this article, we present a parsimonious numerical model based on the cloning of polyps, using five key parameters to simulate a range of coral shapes. The model is agent-based, where each polyp represents an individual. The colony’s surface expansion is dictated by the growth mode parameter ( s ), guiding the preferred growth direction. Varying s facilitates the emulation of diverse coral shapes, including massive, branching, cauliflower, columnar and tabular colonies. Additionally, we introduce a novel approach for self-regulatory branching, inspired by the intricate mesh-like canal system and internode regularity observed in Acropora species. Through a comprehensive sensitivity analysis, we demonstrate the robustness of our model, paving the way for future applications that incorporate environmental factors, such as light and water flow. Coral colonies are known for their high plasticity, and understanding how individual polyps interact with each other and their surroundings to create the reef structure has been a longstanding question in the field. This model offers a powerful framework for studying these interactions, enabling a future implementation of environmental factors and the possibility of identifying the key mechanisms influencing coral colonies’ morphogenesis.

Seagrass meadows are natural carbon sinks, and their conservation and restoration play a crucial role in climate change mitigation and adaptation. However, blue carbon projects are hindered, in most nations, by major gaps in understanding the distribution and extent of seagrasses. Here, we show how satellite tracking of green turtles ( Chelonia mydas ) provided a major advance in identifying novel seagrass blue carbon resources in the Red Sea. By tracking 53 nesting green turtles, we identified 38 distinctive foraging sites. All ground-truthed foraging sites (100%) identified a seagrass meadow, surpassing the 40% ( n = 30) accuracy of satellite imagery-based inferences. Sampling from these turtle-derived locations represents a greater range of depths than previously sampled in the Red Sea providing a carbon stock estimate of 4.89 ± 0.83 kg C _org (organic carbon) m ⁻² . By improving estimates of seagrass extent and associated blue carbon, our approach can support the conservation of blue carbon resources in data-deficient regions worldwide.

Symbiotic dinoflagellates from the family Symbiodiniaceae play a central role in coral reef ecosystems by forming mutualistic relationships with reef invertebrates, particularly stony corals. These relationships underpin reef productivity in nutrient-poor waters but are vulnerable to disruption from marine heatwaves and climate change. While laboratory culturing of symbionts has enabled controlled studies of thermal stress, prolonged culturing may lead to physiological changes that do not reflect in hospite conditions. Here, we examined the thermal stress responses of two axenic cultures of Symbiodinium A1, freshly isolated and long-term cultured (2.5 years), originally from the jellyfish Cassiopea andromeda in the Red Sea. Both cultures were exposed to a daily temperature increase of 1 °C, up to 37 °C. Freshly isolated symbionts consistently showed higher photochemical efficiency (0.515 ± 0.007) and growth rates (1.68 ± 0.60 µ day⁻¹) compared to long-term cultured cells (0.401 ± 0.007; −2.25 ± 0.38 µ day⁻¹), which collapsed at 37 °C. Heat stress also led to decreases in O₂ and increases in pCO₂ across treatments. Long-term cultured symbionts exhibited greater lipid body accumulation, suggesting a shift to anaerobic metabolism. These findings demonstrate that extended batch culturing alters symbiont physiology and stress responses, highlighting the need to consider culture history in experimental designs to avoid bias in interpreting holobiont resilience.

The Red Sea remains one of the least explored deep-sea regions globally, with limited information on the diversity, distribution, and behaviour of fish fauna below the surface mixed layer. During the 2022 Red Sea Decade Expedition, remotely operated vehicle (ROV) surveys were conducted along the Saudi Arabian Red Sea (16.29°–29.37°N), providing extensive visual records of fish communities between 38 and 1,783 m depth. From over 1,000 frame grabs totaling 372.8 hours of ROV footage, 143 unique taxa representing 53 families and 93 genera were identified. Among these, 21 species were confirmed as Red Sea endemics, while 50 taxa exhibited extended depth and/or distributional ranges. Novel in situ behaviours, such as benthic resting, burrow dwelling, and predation, were documented, providing rare ecological insights into demersal fish interactions along the continental slope. Despite limitations in image resolution and species identification, this dataset markedly expands current knowledge of fish diversity and behaviour below the surface mixed layer in the Red Sea. The findings underscore the value of opportunistic ROV observations in revealing hidden biodiversity and establishing a visual reference baseline for future taxonomic and ecological research in the region.

Coral bleaching and mortality are commonly associated with heat stress during marine heatwaves (MHWs), yet attributing these responses solely to heat stress may overlook the complexity of contemporary MHWs. Here, we document a severe MHW affecting a central Red Sea reef in mid‐2024 that coincided with repeated nighttime low‐oxygen events. By integrating satellite and in situ records of temperature, dissolved oxygen and wind, alongside repeated surveys of in situ nursery‐reared coral fragments, we document the temporal coincidence of these conditions with rapid coral bleaching and mortality. As temperatures approached and exceeded 33°C during the MHW peak, nighttime oxygen minima were extreme (down to 15.2–57.8 μmol O ₂ kg ⁻¹ ) and diel temperature variability diminished (down to 0.31°C–0.67°C), indicating a loss of nighttime thermal reprieves. Coincident responses of nursery corals were atypical, with transitions from healthy or bleached states to mortality occurring within 7–8 days. Bleaching and mortality also occurred across diverse coral species in nearby habitats after the MHW peak, with < 1% live coral cover documented eight months later. Sustained high temperatures, reduced vertical mixing and increased nighttime respiratory demand likely constrained oxygen availability, resulting in low‐oxygen extremes. We posit that similar compound MHW extreme events may have gone undetected in the Red Sea and elsewhere, potentially obscuring the contribution of co‐occurring low‐oxygen extremes to coral responses attributed to heat stress.